U.S. patent number 4,660,110 [Application Number 06/548,515] was granted by the patent office on 1987-04-21 for magnetic disk storage device with shroud enclosing disk assembly.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Masayuki Fujii, Masanobu Honda, Muneo Iida, Toshinori Kazama, Jiro Mochida, Nobuyuki Okamoto, Jyosei Simizu, Masami Suzuki, Seiji Tada.
United States Patent |
4,660,110 |
Iida , et al. |
April 21, 1987 |
Magnetic disk storage device with shroud enclosing disk
assembly
Abstract
A magnetic disk storage device capable of avoiding the
occurrence of vibration of magnetic disks and off-track of magnetic
heads with respect to the magnetic disks, including an inner shroud
enclosing a disk assembly composed of a multiplicity of magnetic
disks stacked in superposed relation with spacers being interposed
therebetween and formed at its outer peripheral wall with first
ports for inserting access arms therethrough and at its top above a
spindle supporting the disk assembly with a second port, a
cylindrical filter for removing dust from air flowing through the
second port of the inner shroud into the interior thereof, and a
dust cover enclosing the inner shroud, actuators and filter. The
provision of the inner shroud is conductive to prevention of
development of turbulent air flow in the vicinity of the magnetic
disks. The inner shroud is further formed at its outer peripheral
wall with a multiplicity of small apertures for releasing heat
generated in the inner shroud to outside, to thereby avoid thermal
off-track of the magnetic heads.
Inventors: |
Iida; Muneo (Odawara,
JP), Simizu; Jyosei (Odawara, JP), Suzuki;
Masami (Yokohama, JP), Okamoto; Nobuyuki
(Odawara, JP), Kazama; Toshinori (Hiratsuka,
JP), Honda; Masanobu (Odawara, JP),
Mochida; Jiro (Yokohama, JP), Tada; Seiji
(Odawara, JP), Fujii; Masayuki (Odawara,
JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
16329308 |
Appl.
No.: |
06/548,515 |
Filed: |
November 3, 1983 |
Foreign Application Priority Data
|
|
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|
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Nov 8, 1982 [JP] |
|
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57-194732 |
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Current U.S.
Class: |
360/97.16;
360/99.12; G9B/17.012; G9B/25.003; G9B/33.042 |
Current CPC
Class: |
G11B
17/038 (20130101); G11B 33/1446 (20130101); G11B
25/043 (20130101) |
Current International
Class: |
G11B
17/038 (20060101); G11B 33/14 (20060101); G11B
25/04 (20060101); G11B 17/02 (20060101); G11B
005/012 () |
Field of
Search: |
;360/97-99 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
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|
|
2264029 |
|
Jul 1974 |
|
DE |
|
2145478 |
|
Mar 1980 |
|
DE |
|
54-154310 |
|
Dec 1979 |
|
JP |
|
Other References
Elliot et al., "Filter Arrangement for Rigid File Internal Air
Circulation," IBM Technical Disclosure Bulletin, vol. 26, No. 2,
Jul. 1983, p. 815..
|
Primary Examiner: Wolf; John H.
Assistant Examiner: Bussan; Matthew J.
Attorney, Agent or Firm: Antonelli, Terry & Wands
Claims
What is claimed is:
1. A magnetic disk storage device wherein data is recorded on and
reproduced from magnetic disks, driven for rotation, by means of
magnetic heads, comprising:
a disk assembly composed of the magnetic disks stacked in
superposed relation with cylindrical spacers interposed
therebetween, said disk assembly being supported by a spindle;
at least one pair of access arms, each access arm supporting one of
the magnetic heads for recording and reproducing the data on and
from the magnetic disks;
at least one pair of actuators, each actuator driving one of the
pair of access arms for moving the magnetic heads supported on the
access arms on surfaces of the magnetic disks;
an inner shroud including a cylindrical outer peripheral wall
enclosing the disk assembly with a predetermined distance between
the outer circumferential surfaces of the magnetic disks and an
inner surface of the outer peripheral wall, an upper cover
providing a cover to a top surface of the cylindrical outer
peripheral wall, a lower cover providing a cover to a bottom
surface of the cylindrical outer peripheral wall, means delimiting
first ports located at the outer peripheral wall in positions
corresponding to the pair of actuators, and means delimiting second
ports located at the upper cover and opening above the spindle, the
inner shroud being formed at its outer peripheral wall with a
multiplicity of small apertures maintaining the interior of the
inner shroud in fluid communication with the outside of said inner
shroud, the multiplicity of small apertures formed at the outer
peripheral wall of the inner shroud extending periodically around
the entire circumference of the inner shroud and at different
elevations of the inner shroud corresponding to the respective
disks of the disk assembly, the multiplicity of small apertures
being located such that each small aperture has its central point
directed against an outer edge of a respective disk of the disk
assembly so as to permit air flow therethrough and to reduce
turbulent air flow within the inner shroud, the multiplicity of
small apertures being arranged such that the apertures which are
located at an intermediate elevation have a larger open area than
the apertures which are located at high and low elevations with
respect to the axis of the spindle, whereby the large open area at
the intermediate elevation enable a large amount of air flow
therethrough so as to enable release of greater amounts of heat
from the intermediate portion of the disk assembly than at the
higher and lower portions thereof, thereby enabling thermal
off-track to be minimized;
a filter located in the vicinity of the second port means at the
upper cover of the inner shroud for removing dust from air flowing
through the second port means; and
a dust cover enclosing the disk assembly, the access arm, the
actuators, the inner shroud and the filter as a unit to avoid the
entry of dust form outside.
2. A magnetic disk storage device as claimed in claim 1, wherein
said actuators are two in number and arranged symmetrically with
respect to the spindle, and wherein said first port means of the
inner shroud comprises two ports, each opening in a position
corresponding to one of said two actuators.
3. A magnetic disk storage device as claimed in claim 2, wherein
said filter is in the form of a cylinder of a larger diameter than
the second port means at the upper cover which is fitted between
the upper cover and an inner wall surface of the dust cover on a
center axis of the spindle.
4. A magnetic disk storage device as claimed in claim 3, wherein
said spacers of the disc assembly are formed with a cylindrical
wall member having an inside and an outside and each formed with a
multiplicity of apertures maintaining the inside and outside of the
spacers in communication with each other whereby the air in the
spacers can be released through the apertures to the outside as the
magnetic disks rotate.
5. A magnetic disk storage device as claimed in claim 4, wherein
the predetermined distance between the inner surface of the outer
peripheral wall of the inner shroud and the outer circumferential
surfaces of the magnetic disks is 3 mm.
6. A magnetic disk storage device as claimed in claim 4, wherein
said actuators comprises linear actuators linearly moving the
access arms radially of the magnetic disks.
Description
BACKGROUND OF THE INVENTION
This invention relates to magnetic disk storage devices, and more
particularly it is concerned with a magnetic disk storage device
capable of avoiding generation of vibration and production of dust
in magnetic disks and magnetic heads and off-track of the magnetic
heads with respect to the magnetic disks.
In order to increase capacity and improve system throughput, a
magnetic disk storage device has in recent years been developed
which comprises a multiplicity of magnetic disks stacked in
superposed relation, and two actuators arranged symmetrically with
respect to a spindle supporting the magnetic disks and having
access to the magnetic disks. This type of magnetic disk storage
device is described in U.S. Pat. No. 4,190,870, for example.
In this type of magnetic disk storage device, the magnetic disks
rotate at high speed or at a speed of rotation in the range between
3000 and 3600 rpm. Thus, currents of air which are large in volume
would flow at high speed in a head disk assembly and cause the
magnetic disks and magnetic heads to vibrate, thereby adversely
affecting operations of recording and reproducing data on and from
the magnetic disks by means of the magnetic heads.
Owing to the high speed at which the magnetic disks rotate, windage
loss might generate heat in the magnetic disk storage device. The
heat thus generated would cause expansions of the magnetic disks
each including a base formed of aluminum and tilting of the spindle
supporting the magnetic disks, with a result that an error would be
made in positioning the magnetic head on a desired track of one of
the magnetic disks of the device.
SUMMARY OF THE INVENTION
A first object of this invention is to provide a magnetic disk
storage device capable of avoiding the vibration of the magnetic
disks and magnetic heads which would be caused by air currents.
A second object is to provide a magnetic disk storage device
capable of avoiding the occurrence of thermal off-track of a
magnetic head with respect to a magnetic disk which would be caused
by changes undergone by the magnetic head and magnetic disk due to
heat generated by windage loss in the magnetic disk device.
One of the outstanding characteristics of the invention enabling
the aforesaid objects to be accomplished is that the magnetic disk
storage device provided by the invention comprises an inner shroud
including a cylindrical outer peripheral wall enclosing a disk
assembly composed of a multiplicity of magnetic disks superposed
one above another with spacers interposed therebetween while being
spaced apart a predetermined distance from an outer edge of the
disk assembly, an upper cover providing a cover to a top surface of
the cylindrical outer peripheral wall and a lower cover providing a
cover to a bottom surface of the cylindrical outer peripheral wall,
the outer peripheral wall being formed with first openings each
located in a position corresponding to one of actuators and the
upper cover being formed with a second opening located above a
spindle, a filter located in the vicinity of the second opening
formed in the upper cover of the inner shroud for removing dust
from a current of gaseous fluid flowing through the second opening,
and a dust cover enclosing the inner shroud, filter and actuators
as a unit to prevent dust from entering the disk assembly from
outside.
Another outstanding characteristic is that the filter is
cylindrical in shape and located between the second opening formed
in the upper cover of the inner shroud and the dust cover and that
the outer peripheral wall of the inner shroud is formed with a
multiplicity of small apertures in positions corresponding to outer
edges of the magnetic disks.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional plan view of the magnetic disk storage device
of the prior art developed by us;
FIG. 2 is a sectional side view of the magnetic disk storage device
shown in FIG. 1;
FIG. 3 is a sectional side view of the magnetic disk storage device
comprising one embodiment of the invention;
FIG. 4 is a sectional plan view taken in the direction of arrows
IV--IV in FIG. 3;
FIG. 5 is a sectional plan view taken in the direction of arrows
V--V in FIG. 3;
FIG. 6 is a diagram in explanation of the magnitude of vibration of
the magnetic disks according to one embodiment of the
invention;
FIG. 7 is a sectional side view of the magnetic disk storage device
comprising another embodiment of the invention;
FIG. 8 is a sectional view of the inner shroud of the magnetic disk
storage device shown in FIG. 7;
FIG. 9 is a side view of the inner shroud in explanation of a
modification of the small apertures formed therein; and
FIG. 10 is a diagram in explanation of the thermal off-track caused
by changes in temperature in the embodiment of the magnetic disk
storage device shown in FIG. 7.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before describing the embodiments of the invention in detail, a
magnetic disk storage device of the prior art will be outlined.
FIGS. 1 and 2 show in a sectional plan view and a sectional side
view, respectively, the magnetic disk storage device invented
previously by us. As shown, the magnetic disk storage device
comprises a multiplicity of magnetic disks 1 stacked in superposed
relation through spacers 16 on a spindle 50 supported on a base 5,
linear actuators 4a and 4b located in diametrically opposed
relation to each other with respect to the magnetic disks 1, a
motor 8 for driving the magnetic disks 1 for rotation by rotating a
pulley 6 connected to a lower end of the spindle 50 through a belt
7, and a dust cover 9 located on the base 5 for enclosing the
magnetic disks 1 and linear actuators 4a and 4b as a unit. The
linear actuators 4a and 4b include carriages 3a and 3b supporting
magnetic heads, not shown, through access arms 2a and 2b,
respectively, at end portions so as to move the magnetic heads on
surfaces of the magnetic disks 1. An air filter 12 of an annular
shape is located in a position of the dust cover 9 above the
spindle 50. Each spacer 16 is formed at an outer peripheral portion
with a plurality of air exhaust apertures 11 enabling air
introduced into the spacer through an upper portion to be
discharged therethrough from the spacer when the spacers 16 are
assembled with the spindle 50. The multiplicity of magnetic disks 1
stacked one above another with the interposed spacers shall be
called a disk assembly.
In the magnetic disk storage device of the aforesaid construction,
rotation of the motor 8 causes the magnetic disks 1 to rotate, and
the magnetic heads supported by the access arms 2a and 2b of the
carriages 3a and 3b respectively have acess to the data storing
surfaces of the rotating magnetic disks 1 to perform recording and
reproducing of data.
Currents of air produced in the dust cover 9 as the magnetic disks
1 rotate will be described. When the magnetic disks 1 rotate at
high speed or at a speed in the range between 3000 and 3600 rpm.,
for example, air flows from the spacers 16 through the air exhaust
apertures toward outer marginal portions of the magnetic disks 1
and causes the pressure in the vicinity of central portions of the
magnetic disks 1 to drop, so that the air flowing out of the
spacers 16 through the air exhaust apertures 11 are drawn by
suction through the filter 12 and air suction apertures 10 formed
in positions above the spindle 50 into the spacers 16, from which
the air is discharged again through the air exhaust openings
11.
As the currents of air flow as described hereinabove, air in the
outer marginal portions of the magnetic disks 1 in the dust cover 9
flows, as indicated by arrows A, in the direction of rotation of
the magnetic disks 1. When the actuators 4a and 4b are located in
diametrically opposed positions with respect to the magnetic disks
1, however, the speed at which the air flows tends to vary on
account of the actuators 4a and 4b and the magnetic disks 1 being
enclosed as a unit by the dust cover 9, and the air currents tend
to flow in turbulent flow due to the existence of the actuators 4a
and 4b.
Research conducted by us into the turbulent flow of the air
currents in the outer marginal portions of the magnetic disks 1 has
revealed that the outer marginal portions of the magnetic disks 1
vibrate vertically. It has been ascertained that when magnetic
disks each including a base formed of aluminum of 2 mm thickness
are rotated at 3600 rpm., the vertical vibration of the outer
marginal portions of the magnetic disks has an amplitude of about
0.1-0.2 mm and aggravates the floating stability of the magnetic
heads which float on a film of air formed on a surface of each
magnetic disk. The turbulent flow of air directly causes springs of
the magnetic heads floating under light load to vibrate, thereby
aggravating the floating stability of the magnetic heads.
Aggravation of the floating stability of the magnetic heads raises
the problem that stable performance of recording and reproducing
operations on the magnetic disks by the magnetic heads is far from
being achieved.
We have invented a magnetic disk storage device which is free from
the vibration of the magnetic disks experienced in the magnetic
disk storage device of the prior art shown in FIGS. 1 and 2.
FIGS. 3-5 show one embodiment of the invention in sectional side
and sectional plan views. As shown, the magnetic disk storage
device comprises a base 5, a multiplicity of magnetic disks 1
stacked in superposed relation on the base 5 and supported by a
spindle 50 with spacers 16 of cylindrical shape formed with
apertures being interposed between the magnetic disks 1, a
plurality of actuators 4a and 4b located in diametrically opposed
positions at different levels with respect to the magnetic disks 1,
a motor 8 driving the magnetic disks 1 for rotation by rotating a
pulley 6 attached to a lower end of the spindle 50 through a belt
7, an inner shroud 13 enclosing within its cylindrical outer
peripheral wall the magnetic disks and spacers which is a
characterizing feature of the invention, and a dust cover 9
enclosing the inner shroud 13 and actuators 4a and 4b as a unit.
The inner shroud 13, which is supported on an inner shroud support
bed 14 on the base 5, is formed with ports 15a and 15b for
inserting access arms 2a and 2b supported on carriages 3a and 3b of
the actuators 4a and 4b, respectively, therethrough into the
interior of the inner shroud 13, and an air inlet port 17 for
introducing air into the interior of the inner shroud 13 through an
air cleaning filter 12 of a larger diameter than the air inlet port
17. As shown in FIG. 4, the inner shroud 13 is circular in cross
section and its inner wall surface is spaced apart a predetermined
distance D from an outer circumferential surface of each magnetic
disk 1 except at portions thereof at which the arm inserting ports
15a and 15b are formed. Thus, the inner shroud 13 encloses the
multiplicity of magnetic disks 1 and the spacers interposed
therebetween, which are supported by the spindle 50 and constitute
a disk assembly, substantially in the entirely.
When the magnetic disks 1 of the magnetic disk storage device of
the aforesaid construction rotates at high speed in the range
between 2400 and 3600 rpm., currents of air generated in the
interior of the inner shroud 13 are discharged through the arm
inserting ports 15a and 15b on the side of the inner shroud 13 and
flow through the air inlet opening 17 formed at a top surface of
the inner shroud 13 and via the air cleaning filter 12 into a space
in each of the spacers between the magnetic disks 1 in the inner
shroud 13.
Currents of air flowing through discharge ports formed at the
spacers in the inner shroud 13 flow along an inner wall surface of
the inner shroud 13 as shown in FIG. 5 before being discharged to
the outside through the arm inserting ports 15a and 15b, so that no
turbulent flow of air occurs in the interior of the inner shroud
13. The air discharged through the arm inserting ports 15a and 15b
impinges on the actuators 14a and 14b and the flow thereof becomes
slightly turbulent. However, no influences are exerted by this
turbulent flow on the magnetic disks 1 and magnetic heads because
it occurs outside the inner shroud 13.
FIG. 6 shows the results of experiments conducted on influences
which might be exerted by the distance D between the inner wall
surface of the inner shroud 13 and the outer circumferential
surface of each magnetic disk 1 to study whether changes in the
distance D might affect the development of vibration in the
magnetic disks 1. It will be clearly seen in the figure that when
the distance D is about 12 mm, the amplitude of vertical vibration
in one direction has a value H of about 20.mu. which is relatively
great in value, when the distance D is 10 mm, it has a value G of
about 10.mu., when the distance D is 6 mm, it has a value F of
about 15.mu., and when the distance D is less than 3 mm, it has a
value E of about 8.mu.. Thus, by reducing the distance D between
the inner wall surface of the inner shroud 13 and the outer
circumferential surface of each magnetic disk 1 to a level below 3
mm, it is possible to minimize the vibration of the magnetic disks
1 in the embodiment of the invention shown and described
hereinabove.
As can be seen in the embodiment described hereinabove, the air
currents inside the dust cover 9 and the air currents inside the
inner shroud 13 flow in convection flow through the air cleaning
filter 12. This enables the air inside the inner shroud 13 to be
kept clean at all times and minimizes the dust which might
otherwise invade the most important floating gaps between the
magnetic disks 1 and the magnetic heads in which the magnetic heads
move in floating movement.
The embodiment of the magnetic disk storage device shown in FIGS. 3
and 4 has achieved the effect of avoiding the development of
vibration in the magnetic disks 1. However, further experiments
have shown that when rotation of the magnetic disks 1 is initiated,
accurate positioning of the magnetic heads with respect to the
magnetic disks 1 is unobtainable, that is to say, off-track of the
magnetic heads occurs due to thermal expansion of the disks. More
specifically, as the magnetic disks 1 are started and begin to
rotate, heat is generated by the rotation of the disks 1 and
remains in the interior of the inner shroud 13 and causes the
magnetic disks 1 to expand, but on the other hand the temperature
of the base 5 remains unchanged, so that off-track occurs. After
lapse of a certain period of time, the heat is released from the
inner shroud 13 through the arm inserting ports 15a and 15b into
the dust cover 9. The off-track is reduced in value when the
temperature in the dust cover 9 or the temperature of the magnetic
heads and magnetic disks 1 in the inner shroud 13 becomes
substantially equal to the temperature in the vicinity of the base
5.
The fact that it takes time for the off-track to be reduced in
value and to disappear has raised the problem that startup of
equipment of a system with which the magnetic disk storage device
is associated would lag behind.
In order to obviate the aforesaid problem, we have developed
another embodiment of the magnetic disk storage device in
conformity with the invention which has the effect of avoiding
thermal off-track. This embodiment will be described by referring
to FIG. 7.
The shroud 130 of this embodiment is formed with a multiplicity of
small apertures 100 in positions along the outer circumferential
surfaces of the magnetic disks 1 and encloses the multiplicity of
magnetic disks 1 in their entirety with a clearance of about 3 mm
between the inner wall surface of the inner shroud 130 and the
outer circumferential surface of each magnetic disk 1. Like the
inner shroud 13 shown in FIGS. 3 and 4, the inner shroud 130 is
formed with the ports 15a and 15b for inserting the access arms 2a
and 2b, respectively, therethrough, and the air inlet port 17 for
introducing into the inner shroud 130 clean air admitted through
the air cleaning filter 12. The provision of the inner shroud 130
inside the dust cover 9 enables air currents flowing about the
magnetic disks 1 as described by referring to FIG. 5 to be
regulated by the inner shroud 130 to flow as indicated by solid
line arrows in FIG. 7 and causes the air in the inside of the inner
shroud 130 to flow in the direction of rotation of the magnetic
disks 1. Exchange of air between the inside and outside of the
inner shroud 130 is achieved by allowing the air in the inside of
the inner shroud 130 to be released therefrom through the ports 15a
and 15b for inserting the arms 2a and 2b and the multiplicity of
small apertures 100 formed at the wall of the inner shroud 130 and
letting clean air introduced into the interior of the inner shroud
130 through the air inlet port 17 via the air cleaning filter
12.
As shown in FIG. 8, the small apertures 100 formed at the wall of
the inner shroud 130 are located in positions corresponding to the
outer circumferential surfaces or outer edges of the magnetic disks
1 located inside the inner shroud 130. This allows air currents
generated by the rotation of the magnetic disks 1 to flow along top
surfaces of the magnetic disks 1 and be released through the small
apertures 100, so that air currents impinging on the inner wall
surface of the inner shroud 130 and rebounding therefrom are very
small in volume.
Inside the inner shroud 130, the temperature at the intermediate
portion is higher than those at higher and lower portions. To
release greater amounts of heat from the intermediate portion than
from the higher and lower portions in the inner shroud 130, those
small apertures 100 which are located at the intermediate portion
may have their diameters or numbers increased, as shown in FIG. 9,
as compared with those small apertures 100 which are located at the
higher and lower portions. The reason why the temperature at the
intermediate portion is relatively high is that the heat of the
higher and lower portions is also released from the upper and lower
covers of the inner shroud 130 as compared with the intermediate
portion, so that a greater amount of heat remains in the
intermediate portions of the inner shroud 130.
The provision of the multiplicity of small apertures 100 at the
wall of the inner shroud 130 enables the thermal off-track to be
minimized while greatly reducing the turbulent flow of air. The
effects achieved by the provision of the small apertures 100 will
be described by referring to FIG. 10.
FIG. 10 is a diagram showing chronological changes in the off-track
phenomenon occurring in the magnetic heads with respect to the
magnetic disks when the inner shroud is formed with apertures and
when the inner shroud is formed with no apertures. In the diagram
shown in FIG. 10, a line X represents a chronological change
occurring when the inner shroud is formed with no apertures, and a
line Y indicates a chronological change occurring when the inner
shroud is formed with apertures. It will be clearly seen in the
figure that when no apertures are formed, the off-track does not
become stable in value until the magnetic disks are driven for
rotation for over one hour, and that when the apertures are formed,
the value of the off-track falls within an allowable range in
several minutes following initiation of rotation of the magnetic
disks. This is accounted for by the fact that the heat generated by
friction between the air and the surfaces of the magnetic disks
during the rotation of the magnetic disks remains inside the inner
shroud when no apertures are formed at its wall, and a temperature
difference is produced between the inside and the outside the inner
shroud, so that it takes time to eliminate the temperature
difference by allowing the magnetic disks to rotate. On the other
hand, when the inner shroud is formed with the apertures, the heat
generated inside the inner shroud is released to the outside
through the apertures and the temperature difference is eliminated
earlier than when no apertures are formed, thereby enabling the
off-track value to become stable in a few minutes.
From the foregoing description, it will be appreciated that the
magnetic disk storage device according to the invention comprises
an inner shroud for enclosing the disk assembly in its entirety
along the outer circumferential surfaces of the magnetic disks and
being formed with a multiplicity of small apertures. The provision
of such inner shroud makes it possible to achieve the effects of
eliminating turbulent flow of air currents and avoiding vibration
of the magnetic heads and the magnetic disks and minimizing the
off-track phenomenon caused by heat generated by the rotation of
the magnetic disks.
In the embodiments shown and described hereinabove, the actuators
of the magnetic disk storage device have been shown and described
as being of the linear movement type. The invention is not,
however, limited to this specific form of actuators and actuators
of the rotary type may also be used without departing from the
scope of the invention.
* * * * *